Influencing factors of slagging on heating surface of boiler
(1) Ash characteristics of pulverized coal
Generally, the softening temperature ST of ash is used as the main indicator of slag formation. Coal with low ash melting point (ST<1200℃) is easy to slag. In addition, the slagging index also includes: silicon ratio, alkali-acid ratio, slagging index, limit viscosity and so on.
（2）Aerodynamic characteristics in the furnace
Improper air flow organization leads to flame center deviation, and the pulverized coal air flow flame adheres to the wall, causing local slagging of the water-cooled wall;
Improper air flow organization, forming flue gas retention vortex area and forming a reducing atmosphere (with CO), reducing the ash melting point and increasing the possibility of slagging.
Excess air coefficient: When the excess air in the furnace is too small, a reducing atmosphere may be generated, and the tendency of slagging will increase accordingly.
（3）Influence of boiler heat lo
1. During the start-up process of the burner, if the burner repeatedly alarms and locks, it should be found out the reason, find the fault and eliminate it, and then press the reset button to inherit the start. Note: The continuous press of the reset button should not exceed 10 seconds
2. If the burner is not successful in one combustion, the natural gas boiler induced draft fan should be restarted, and the second combustion can be started after 5 minutes of ventilation.
3. In the normal operation era, the burner close to the thermal equipment department (such as the connecting flange, etc.) will be very hot, to prevent the formation of burns. Do not place flammable materials in the vicinity to avoid causing fire.
4. During the operation of natural gas-fired boilers, it is necessary to closely supervise the working conditions of hot water circulation pumps and natural gas-fired boiler pressures, natural gas distribution bags, pipeline valves, pressure gauges, flow meters, and water
Industrial boilers will produce wastes that needs to be treated during the use process, which is what we mentioned of boiler blowdown. What are the methods for boiler blowdown?
1. Regular blowdown
1) The time interval and quantity of discharge depend on the test results of boiler water. It usually do not exceed 5% of the water supply.
2) When the regular blowdown is being made under high load of the boiler, the blowdown of the water-cooled wall header is generally not required to avoid affecting the normal water circulation of the water-cooled wall and forming a tube explosion incident.
2. Continuous blowdown
The amount of blowdown shall be determined according to the test results of the boiler water, and shall be completed by adjusting the needle-shaped angle of the blowdown tube.
The fuel of a gas-fired boiler is gas such as natural gas, city gas, biogas and liquefied gas, etc. What kind of fuel the boiler burns is decided by an equipment called a burner. The boiler equipped with a gas-fired burner is called a gas-fired boiler. There are three methods of gas-fired boiler combustion as per technical characteristics of how the gas and air mix.
1. Diffusion combustion:
Gas and air mutually diffuse at the gas nozzle and are burning. The advantages are burning stably and with simple burner structure. However, the heated area is easy to be carbonized due to long flame, which is easy to produce incomplete combustion.
2. Premixed combustion:
A part of air and gas are premixed before combustion (coefficient of primary air surplus is between 0.2-0.8), and then being burned. The advantages are clear combustion flame, enhanced combustion, and high thermal efficiency.
The explosion-proof door of the gas-fired boiler is opened or broken when the combustible gas explosion suddenly increases the pressure, it then releases high-pressure gas to reduce the damage to the gas-fired boiler body and also ensure
The function of the gas-fired boiler explosion-proof door is usually reflected when the gas-fired boiler is ignited or running due to improper operation. For instance, the furnace is not purged before ignition, the furnace is still not purged even the ignition cannot successfully be lit, the nozzle is leaking, the fuel is not completely burned, and extinguished failure to cut off fuel quickly, etc. all of them may cause the furnace and tail flue to explode. Installing explosion-proof door for gas-fired boiler is to release the pressure to avoid the accident from expanding and also to ensure the safety of the industrial steam boiler when a slight explosion occurs in the furnace or flue.
Here load means, amount of steam drawn from the boiler. So when the load increases, the specific volume of the steam in the boiler increases reducing the pressure. This inturn demands for more feed water and more amount of fuel to be burnt. So, for any boiler there will be a feed water level control system put in place to measure the water level in drum. As and when the level of water in the drum reduces, the controller sends a signal to the feed water pump to start and stops when the desired water level is reached. This way the steam generation continues to maintain the desired pressure.
A water level sensor fail on a steam boiler is extremely dangerous. The low water cut of should be tested daily. If the sensor fails the boiler could turn all the water into steam, leaving the boiler dry. Without water in the boiler the flame from the burner would heat up the heating surface to extreme temperatures and would crack and damage the inside of the boiler. But that’s not the dangerous part. If water added to boiler while it is extremely hot. Once water touches the extremely hot heating service, water would immediately start to evaporate into steam. When water evaporates it expands 18x it’s original size. The boiler would explode from the sudden increase in pressure from the inside. Some in some cases, boilers that have exploded out of a building and have landed 100s of feet away.
Not inspecting it often enough can lead to minor issues being missed, which can lead to major issues later and possibly injury.
Not checking a boiler system could have catastrophic results in the form of a boiler explosion. Fuel may explode due to unfound problems. The high temperatures generated by the boiler can also cause problems if the water level drops too low and the trip switch fails.
